WDPN31 PGTW 280900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 20W (MINDULLE) WARNING NR 024//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.7N 135.7E
   INITIAL INTENSITY: 95 KTS
   GEOGRAPHIC REFERENCE: 360 NM WEST-SOUTHWEST OF IWO TO
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 45 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TY 20W SEEMS TO STILL BE STRUGGLING TO REINTENISFY AFTER BEING
KNOCKED LOW BY THE RECENT EYEWALL REPLACEMENT CYCLE (ERC) AND THE
EFFECTS OF UPWELLING.  ANIMATED MULTISPECTRAL SATELLITE IMAGERY
(MSI) DEPICTS A RAGGED, ROUGHLY 30 NM WIDE EYE, THOUGH BOTH THE
SUBJECTIVE AND OBJECTIVE FIXES ARE BEGINNING TO SCATTER AS THEY
STRUGGLE TO LOCATE A PRECISE CENTER. A PICTURESQUE 280409Z AMSR2
89GHZ MICROWAVE IMAGE SHOWED AN INNER BAND OF WEAK CONVECTION IN
THE MIDDLE OF A QUITE LARGE OUTER BAND OF MORE SIGNIFICANT
CONVECTION. LATER ENHANCED INFRARED IMAGERY SHOWS DEEP CONVECTION
AND VERTICAL HOT TOWERS FLARING UP ON THE UPSHEAR (SOUTHWEST) SIDE
OF THIS OUTER BAND AND WRAPPING CLOSER TO THE CORE, POSSIBLY
INDICATING THAT FINALLY, THE CORE MAY START CONSTRICTING ONCE MORE
AND START THE LONG-AWAITED REINTENSIFICATION. THE INITIAL POSITION,
DUE TO THE RAGGED NATURE OF THE EYE, IS ASSESSED WITH ONLY MEDIUM
CONFIDENCE. THE INITIAL INTENSITY REMAINS ASSESSED AT 95 KNOTS WITH
MEDIUM CONFIDENCE JUST SLIGHTLY BELOW THE ADT AND SATCON AND AT THE
MEDIAN OF THE AGENCY CURRENT INTENSITY ESTIMATES, THOUGH THE AGENCY
DATA-T NUMBERS WERE FAR LOWER, WITH PGTW AND KNES AT T4.5. THE
SYSTEM IS NOW MOVING NORTHWEST AT ABOUT 8 KNOTS, TAKING IT OVER A
BETTER OCEANOGRAPHIC ENVIRONMENT AND AWAY FROM THE COLD POOL.
OTHERWISE THE ENVIRONMENT IS VERY FAVORABLE, WITH LOW SHEAR, AND
ROBUST RADIAL OUTFLOW. THE INITIAL WIND RADII HAVE BEEN ADJUSTED
ABOUT 20 PERCENT LARGER BASED ON A THE AMSR2 WINDSPEED PRODUCT FROM
280409Z.

INITIAL WIND RADII BASIS: OTHER. 280409Z AMSR2 WINDSPEED PRODUCT. 

CURRENT STEERING MECHANISM: NORTHWEST PERIPHERY OF BUILDING
SUBTROPICAL RIDGE (STR) TO THE SOUTHEAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.0 - 90 KTS
   RJTD: T6.0 - 115 KTS
   RCTP: T5.5 - 102 KTS
   KNES: T5.0 - 90 KTS
   CIMSS SATCON: 106 KTS AT 280358Z
   CIMSS ADT: 102 KTS AT 280540Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG RADIAL

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: HIGH

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING. HOWEVER THE FORECAST HAS
BEEN TRUNCATED TO 96 HOURS DUE TO EXTRA-TROPICAL TRANSITION. 

FORECAST DISCUSSION: THE MAJORITY OF GLOBAL MODEL FIELDS AND JMA
UPPER-LEVEL ANALYSIS CHARTS INDICATE THAT THE BLOCKING RIDGE TO THE
NORTH HAS ERODED AND RETREATED WESTWARD, AND THUS THE STR TO THE
SOUTHEAST HAS BECOME THE DOMINANT STEERING MECHANISM. THUS, TY 20W
HAS STARTED MOVING NORTHWEST AT A FAIR CLIP OVER THE PAST SIX
HOURS. IT IS FORECAST TO CONTINUE TO ACCELERATE, SLOWLY AT FIRST,
THEN AT A GRADUALLY INCREASING PACE, THROUGH THE NEXT 24 TO 36
HOURS. AS THE RIDGE TO THE EAST REORIENTS TO A NORTH-SOUTH AXIS, TY
20W WILL IN RESPONSE TURN NORTHWARD. THE SYSTEM THEN TURNS NORTHEAST
AND ACCELERATES SHARPLY AFTER TAU 36 AHEAD OF A MID-LATITUDE TROUGH
RAPIDLY APPROACHING FROM THE WEST. A SURFACE LOW AND COLD FRONT
ASSOCIATED WITH THIS MID-LATITUDE SYSTEM WILL DRAG ACROSS THE SEA
OF JAPAN AND LIE ROUGHLY ALONG CENTRAL HONSHU BY TAU 48. BY TAU 72,
TY 20W WILL APPROACH AND BEGIN INTERACTING WITH THIS BAROCLINIC ZONE
AT THE SURFACE, AND START TO BECOME ABSORBED UNDER THE ASSOCIATED
UPPER-LEVEL TROUGH, MARKING THE START OF EXTRA-TROPICAL TRANSITION
(ETT). BY TAU 84 THE SYSTEM SHOWS MARKED THERMAL ADVECTION WITH
STRONG, COLD, DRY, NORTHWESTERLY WINDS PUSHING SOUTH FROM HONSHU
AND WRAPPING INTO THE CORE OF THE SYSTEM. THE ETT PROCESS IS
FORECAST TO BE COMPLETE BY TAU 96 WITH THE SYSTEM DEVELOPING
WELL-DEFINED COLD AND WARM FRONTS AND EMBEDDED UNDER A 500 MB LOW
HEIGHT CENTER. WHILE THE TRACK IS FORECAST TO REMAIN OFFSHORE AND
BE UNDERGOING ETT AS IT PASSES YOKOSUKA, STRONG GALE FORCE WINDS
CAN BE EXPECTED OVER EASTERN HONSHU, PARTICULARLY AS THE SYSTEM
PASSES AND THE STRONG GRADIENT-INDUCED WINDS BETWEEN TY 20W AND THE
TRANSIENT HIGH PRESSURE SYSTEM MOVING IN BEHIND THE SYSTEM DEVELOP
OVER EAST-CENTRAL HONSHU.   

MODEL DISCUSSION: TRACK GUIDANCE IS IN VERY GOOD CROSS-TRACK
AGREEMENT THROUGH THE FORECAST PERIOD, WITH MINIMAL SPREAD OF 65 NM
AT TAU 48, INCREASING TO 130 NM AT TAU 96. ALONG-TRACK SPREAD
UNSURPRISINGLY INCREASES STEADILY AFTER TAU 48, TO 220 NM BY TAU
120. THE JTWC TRACK REMAINS CONSISTENT WITH THE PRIOR FORECAST WITH
HIGH CONFIDENCE THROUGH THE DURATION. THE BULK OF THE INTENSITY
GUIDANCE IS IN FAIRLY GOOD AGREEMENT, THOUGH THE COAMPS-TC FAMILY
ARE DISSENTING, AND SHOWING STEADY WEAKENING FROM TAU 00. THE
REMAINDER OF THE GUIDANCE SUPPORTS THE SHAPE OF THE INTENSITY CURVE
IT SHOULD BE NOTED THAT THE RAPID INTENSIFICATION PREDICTION AID
(RIPA) HAS BEEN TRIGGERED FOR THE SECOND CONSECUTIVE RUN,
INDICATING A NEAR-TERM RI TO 135 KNOTS BY TAU 24. AT THIS POINT,
WHILE THE AID IS TRIGGERING, THE CONSTITUENTS OF IT, INCLUDING THE
MID-LEVEL HUMIDITY, SST POTENTIAL AND 200 MB DIVERGENCE ARE ALL
NEUTRAL OR UNFAVORABLE FOR RI. THUS WHILE THE SYSTEM IS EXPECTED TO
INTENSIFY, IT IS NOT EXPECTED TO RI AT THIS TIME. THE JTWC FORECAST
TRACES THE INTENSITY CURVE, BUT SITS ABOUT 10 KNOTS HIGHER THAN THE
CONSENSUS MEAN AND ABOVE ALL THE GUIDANCE THROUGH TAU 48, THEN
CLOSELY TRACKS THE MEAN THEREAFTER, WITH MEDIUM CONFIDENCE.  

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   TRACK 72-120 HR: HIGH
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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